ZyXEL Communications VES1724-56 User Manual page 99

interference to the Line 2. CO receives signal with higher attenuation. With UPBO enabled on the
CPE (A), it decreases the PSD level and reduces the crosstalk impact on long loops.
Figure 51 UPBO Resolves Upstream Far-End Crosstalk
CPE (B)
DPBO
VDSL signal may interfere with other services (such as ISDN, ADSL or ADSL2 provided by other
devices) on the same bundle of lines due to downstream far-end crosstalk. DPBO (Downstream
Power Back Off) can reduce performance degradation by changing the PSD level on the VDSL
switch(es) at street cabinet level.
ISDN in Europe uses a frequency range of up to 80 kHz, while ISDN in Japan uses a frequency
range of up to 640 kHz. ADSL utilizes the 1.1 MHz band. Both ADSL2 and ADSL 2+ utilize the 2.2
MHz band.
An example is shown next. VDSL Line 1 and ADSL Line 2 are in the same binder. Crosstalk occurs
when the ADSL signal flows from CO (B) and is near to CO (A)'s ONU (Optical Network Unit)
location. Besides, higher Line 1 PSD causes higher interference to the Line 2. CPE (B) receives
VES1724-56 User's Guide
CPE (A)
No-UPBO
UPBO
Line2 (600m)
Central
Site (CO)
Line1 (150m)
Chapter 9 VDSL Setup
99